Bossert et al. in U.S. Pat. No. 4,048,171 disclose cardiovascular agents of the formula ##STR2## wherein R is hydrogen, straight, branched or cyclic lower alkyl, lower alkenyl, or lower alkinyl, unsubstituted or substituted; or benzyl, or phenethyl, unsubstituted or substituted in the aryl portion;
R' is alkyl of 1 to 4 carbon atoms; PA1 R" is alkenyl of 2 to 6 carbon atoms, alkynyl of 2 to 6 carbon atoms, cyclic alkenyl of 3 to 6 carbon atoms interrupted by oxygen, alkenyl of 2 to 6 carbon atoms or alkynyl of 2 to 6 carbon atoms interrupted by 1 or 2 oxygen atoms, or alkenyl of 2 to 6 carbon atoms or alkinyl of 2 to 6 carbon atoms substituted by hydroxyl; and PA1 R"' is unsubstituted or substituted aryl; cyclohexyl; benzyl; styryl; pyridyl; pyrimidyl; furyl; thienyl; pyrrolyl; pyridyl; pyrrolyl, thienyl or furyl substituted by alkyl of 1 to 2 carbon atoms; or substituted pyrimidyl. PA1 R.sub.4 is heterocyclo, mono substituted phenyl wherein said substituent is selected from the group consisting of lower alkyl of 1 to 4 carbons, halo, CF.sub.3 and nitro, or disubstituted phenyl wherein said substituents are selected from the group consisting of methyl, halo, CF.sub.3, and nitro; PA1 R.sub.5 and R.sub.6 are independently selected from the group consisting of hydrogen, lower alkyl, --(CH.sub.2).sub.m --aryl, ##STR9## or R.sub.5 and R.sub.6 taken together with the N-atom to which they are attached complete a heterocyclic ring of the formula ##STR10## R.sub.7 is hydrogen, lower alkyl, --(CH.sub.2).sub.m --aryl or a pharmaceutically acceptable salt forming ion; PA1 R.sub.8 is hydrogen, lower alkyl of 1 to 4 carbons, lower alkoxy of 1 to 4 carbons, lower alkylthio of 1 to 4 carbons, halo, CF.sub.3, nitro, or hydroxy; PA1 R.sub.9 is hydrogen, lower alkyl of 1 to 4 carbons, ##STR11## R.sub.10 is lower alkyl of 1 to 4 carbons, ##STR12## A.sub.1 is ##STR13## A.sub.2 is ##STR14## m is zero or an integer from 1 to 6; n is an integer from 1 to 6; PA1 p is zero, one or two; PA1 R.sub.13 and R.sub.14 are independently selected from the group consisting of hydrogen, lower alkyl of 1 to 4 carbons, ##STR15## and --(CH.sub.2).sub.r --cycloalkyl; R.sub.15 is lower alkyl, aryl, cycloalkyl, --A.sub.1 --aryl, --A.sub.1 --cycloalkyl, --A.sub.1 --heterocyclo, --A.sub.2 --OH, --A.sub.2 --O--lower alkyl, --A.sub.2 --O--(CH.sub.2).sub.m --aryl, --A.sub.2 --SH, --A.sub.2 --S--lower alkyl, --A.sub.2 --S--(CH.sub.2).sub.m --aryl, ##STR16## halo substituted lower alkyl, or ##STR17## and, r is zero or an integer from 1 to 3. PA1 R.sub.15 is straight or branched chain lower alkyl of 1 to 5 carbons, benzyl, ##STR29## R.sub.1 is lower alkyl of 1 to 5 carbons, lower alkenyl of 3 to 5 carbons or benzyl; PA1 R.sub.2 is straight or branched chain lower alkyl of 1 to 5 carbons, especially methyl; PA1 R.sub.3 is straight or branched chain lower alkyl of 1 to 5 carbons, benzyl, ##STR30## R.sub.4 is mono substituted phenyl wherein said substituent is selected from lower alkyl of 1 to 4 carbons, halo, CF.sub.3, or nitro, disubstituted phenyl wherein said substituents are selected from methyl, halo, CF.sub.3 and nitro, 2-, 3-, or 4-pyridinyl, 2-methylthio-3-pyridinyl, or 2, 1, 3-benzoxadiazolyl; PA1 A.sub.2 is --CH.sub.2 --(CH.sub.2).sub.n -- or ##STR31## n is 1, 2 or 3; R.sub.5 and R.sub.6 are independently selected from hydrogen, straight or branched chain lower alkyl of 1 to 5 carbons, benzyl and --(CH.sub.2).sub.m --aryl, or R.sub.5 and R.sub.6 taken together with the N atom to which they are attached complete a heterocyclic ring of the formula ##STR32## R.sub.9 is methyl, benzyl, or diphenylmethyl; and, R.sub.10 is benzyl or diphenylmethyl. PA1 R.sub.15 is methyl, ethyl, isopropyl, benzyl, ##STR33## R.sub.1 is methyl, pentyl, 2-propenyl or benzyl; R.sub.2 is methyl; PA1 R.sub.3 is ethyl, isopropyl, 1-methylpropyl, ##STR34## and, R.sub.4 is 2-nitrophenyl, 3-nitrophenyl, 2-chlorophenyl, 3-chlorophenyl, 2-(trifluoromethyl)phenyl, 3-(trifluoromethyl)phenyl, 2,3-dichlorophenyl, 2-chloro-3-nitrophenyl, or 4-(2,1,3-benzoxadiazol)-yl.
Stoltefuss et al., in German Offenlegungschrift No. 3,234,684 A1, disclose dihydropyrimidines of the formula ##STR3## wherein R.sub.5 is hydrogen, alkyl, substituted alkyl, phenyl, etc. These compounds possess cardiovascular activity.
Cho, et al, in European Application No. 0,157,219 A1, disclose dihydropyrimidine compounds useful as cardiovascular agents having the formula ##STR4## wherein R.sub.1 is methyl or ethyl, R.sub.2 is methyl or ethyl, R is phenyl or substituted phenyl and X is chloro or methyl.